you're certainly aware that libgit2 is a reimplementation of git, largely sponsored by github since the original git libraries are binding-unfriendly to say the least. The de-facto ruby "bindings" (grit) were a mere wrapper around cli git and afaik this used to be the only way to go.

I tried to use libgit2 for a project last year and a coworker did a couple of patches and I can say that there's still a lot of ground to cover until libgit2 is at least somewhat feature complete. Back then, clone via SSH and other _must_have_ features were unimplemented.